Figai 
Bn (4 


ELECTRIC IGNITION FOR AUTOMOBILE ENGINES 


YOSO NAITO 


Sendai Kogakushi, Tohoku Imperial University, 1913 


THESIS 


Submitted in Partial Fulfillment of the Requirements for the 


Degree of 


MASTER OF SCIENCE 


IN ELECTRICAL ENGINEERING 


THE GRADUATE SCHOOL 
OF THE 


UNIVERSITY OF ILLINOIS 


1921 


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Kity) PRAIA 


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UNIVERSITY OF ILLINOIS 


THE GRADUATE SCHOOL 


ee ag 197) 


I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY 


SUPERVISION By____Yoso Naito 


ENTITLED __ ELECTRIC IGNITION FOR AUTOMOBILE ENGINES _ 


BE ACCEPTED AS FULFILLING THIS PART OF THE REQUIREMENTS FOR 


THE DEGREE OF MASTER OF SCIENCE IN ELECTRICAL #NGINEERING 


oud P vie 


In Charge of Thesis 


Recommendation concurred in* 


Committee 


on 


Final Examination* 


*Required for doctor’s degree but not for master’s 


49383537 


Digitized by the Internet Archive 
in 2015 


https://archive.org/details/electricignitionOOnait 


Contents 


Ignition Circuit 


Introduction .... 
Fundamental Principles of Ignition 
PMS Meme so as. ea, ESS, RI DPI eG 


Phenomena of Closing the Interrupter 5 


Phenomena of Opening the Interrupter 16 


Interrupter Sperk 
Opening the Interrupter When the 


Secondary Current is Appreciable ....32 


Heat Energy of Various Ignition 


Systems eoseeoesetersxr8e2 708 BORER Bs 


abee fated 


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—— = oP 


ELECTRIC IGNITION FOR AUTOMOBILE ENGINES 


Part I Ignition Circuit 


Introduction 


Automobile €nginéering has made great progress during 
the past few years. The new devices of yesterday to-day 
are commonplace. 

As for spark ignition, there still exists much dis- 
cussion about the relative merits of the battery and magneto 
systems. 

The phenomenon of the electric spark was considered 
by Faraday many years ago. But a perfect analysis of spark 
has not yet been given. 


The object of this thesis is to study the electrical 


phenomena of the primary and the secondary circuit of ig= 


nition apparatus.at the instant of sparking. 

For mathematical analysis the battery ignition is 
taken, but we may apply the same theory for magneto ignition 
by Slight modifications. 

The latter part of this thesis deals with the heat 


quémtity in @ single spark of the various ignition systems. 


II Fundamental Principles of Ignition 


Systems 


In developing the theory, the schematic coil show 


in Fig.! will be considered. 


Fig. 1 
Primary terminal voltage 
Primary and secondary currents 
Primary and secondary Inductances 
Primary and secondary resistances 
Primary and secondary capacities 


Interrupter 


§.G. Spark Gap M Mutual inductance 


The fundamental equations of the circuit Shown above 
are: 


For the primary circuit, 


ft 
ha 


iv 


where 
The differential equations for the primary and the 
secondary currents respectively are reduced from equations 


()) and (22. 


we 


fel 


oP Aeon fel a. 


A%, dig 
(I ae Sat cles nuit 


a ee Ete tee 
(See Appendex I) 

The complete integrations of these fourth order dif- 
ferential equations can be accomplished, but is of minor 
interest. 

To avoid the complication, we shall study the phenomena 
for definite positions of the interrupter and consider the 


primary and the secondary resistance, ,inductance, and cap 


acity constant in most cases. 


vas Wp) ee yz SEF 3s Te] 
7 ay 7 7 


s¢ 
ir \S) 4 


rit Phenomena of closing the interrupter 


To speak rigorously, a secondary charging current 
exists in the secondary circuit in this case, but we shall 
neglect this current. 

No voltage is impressed on: the primary condenser, be- 
cause the interrupter is closed. So My se and ee 

7 


are both zero. 


The equation (1) page3 becomes 


£ + t, St 


be es 
4, 


£ 


_ 2 


= ao 
an FE 
O sew 


eae 


7 


which is known as the Helmholz 


The instantanious primary voltage 


' LL 
a, 7 ast. is 
& = Mee = +4- Li (OZ 2 ) FP 


& 
a am 
S/N “) 


The following numerical constants are given for the 


e 


Connecticut Igniter Model-16 : 


AAO) 
~ 
> 


s .. 


Tet ot Igniter Mod-/é 


L, Ott henry 
a 1.1 ohms ry, 10,000 ohms 
C «25 micro-farad C2 smaller than .O00O1m.f.!} 


The relation between time and the primary current 


culculated by equation(6) is> shown in the following table. 


Table 1 Growth of the primary current 
I Sine amperes 


1.1 ohms 


eO1t henry 


= 5-725 volts 


log e log 2-72 = .434 


Lf 


i ) te ’ ie 4 7 }} 
ee en ene Soe eT ee NV OREL ONT i) i eae es te 


tmerncisn praganlbenyy. aia Bell ah da eee wd: 
seLtos, RoteoR Set wel it \rhecmite a @ : 


2%9 a yc : . his = 
amito” ” hi ni 
yin t 


TY) a HY 


« 
%. 
od ? 
\ | 
a 
’ 
. 
. 
’ 
i 
~ 
, 
,% 
Py 
#e 
> 
' ra 4 
s 
Sie 
> an a ee 


The curve corresponding to Table 1 is shown in Fig.6, 
page 13. Its oscillogram which is taken by author is 


seen below. 


Wiad, Ciurponrt= FR 
C3Z0rpLn,. JTun Speed 


Enter’ pres ae 


Fig. 3 

If we enlarge this oscillogram and plot a curve 
Fig.6,rpage 15, there is seen a-c@rtain difference from 
Curve A. Probably this difference depends upon the fact that 
magnetization curve of ironis not a straight line’ and con- 
consequently the primary inductance is not constant. 

We Will now consider the case when the primary induc=~ 
tance is not constant. 

Te values of the following”table are taken from the 
oscillogran. 

TapLewe 


1, 
ampere 


Glosing the Interrupter in the Case 


of Variable Inductance: 


In the former discussion’, we assumed that the induct- 
ance l,is constant, while it is variable with any circuit 
which contains an iron core. The variation of inductance 
depends upon the magnitude of the air gap and the quality 
of the iron. 


An example of the saturation curve of an entirely 


-losed ferro-magnetic circuit is shown in Fig.(4). 


Exatihg current 
in Gp. 


i eee ae 
Pew mlaeke fry A, 


\ . San") aHi7y 


Hi 


10 

If the magnetic circuit consists partly of air and 

partly of iron, the saturation curve is modified by the 
influence of air gap. 

When the air gap is very small, the corresponding 

curves: are a and b, Fige5. If the gap becomes larger, 


saturation curve approaches the dotted line, and the 


hysteresis loop vanishes. 


hnes 


9 
y 
§ 
eS 
x 
& 


Frolich’s equation for such a saturation curve, which 


is modified by Kennelly, is shown below. 


where # = flux 


where N:: number of turns 


The equation (i), page 3 becomes 


a. 


Ne iy A Or ay? te ee 


oor ‘el gy te enh ey 


| ‘ AIBA bs bat 
ii a DAs ee hig 


r 
ce a 


4 py 
‘ : a Lima st abit Be a it 


rey i 


’ 
4 


i ig Met Ft 
i Ot ae oi 
vy = 


AK dé 
Crki)* dt 


Land 


(the dt 


The variables are separable in the above equation. 


dL 
(E- cA) +k i)? 


SO Se ome ger ye 
(E-cry( 14+ hke)* — A” 


mia ? AL 
=f ————_ ore + | 
J ae (E-<r)a* ; (/+he)a 


=r Meal Ar a a c aW=- A ) 2 
Adie dt 3e@ . ppendex ) 


oe NTE) eee lagli+ke) - Qa rs 


© 7 mae 


Ae 
Tee 


( Berg. s Advanced Course of Electrical 
Engineering) 


The variable inductance for the corresponding values- of ex- 


citing current i is measured forza certain coil which has 
an open iron core. Then, we may find the constants k and 
A. Using these constants, we will study how the current 


bullds up in, the coil considered in the previous article. 


. hw 
) 
my ny 
a 
ea °% >». 
\ 
‘ 
. 
” 
\ ~ 
7 ek 
i Ag 4 
aw 
- q ( ei t J 
7 mY. elite aes oii aw, ae 
1a 
} 4 


Oi isha ich ai Aaa aa eae Ms 


est)» Sj ri te ays Y on pe rae 
a OSH Dhol 24k Ayres et hy 


12 
By the equation (9), 


z rng ee log E = tke, ey is } 


E 537125 
2.01018 r, 1.1 
a=r+khk =1.14+5.725x .1128 
= 1.745 


So, the above equation becomes 


_ 1040/8 hy, ey yeas LEIS 
ae: 1,74AS 1, VAS “4 Ease ge Te S.JZ5 —+/¢ 


if Wi ee 
VEGA IOC 


a t= .c05etx} 1.45 lag L2EEUEUEES 31/22 2 (40) 


SIZE —hl J+ .AI(2B4 


Table 3 is calculated by the equation (10). 


Table 3 


: r ' 
L A=Zlogr Lthe a 


2-2 
ampere 4 


200176 
200358 
0057 

00853 


.01087 
00157 


The corresponding curve to this table is shown in 


Fig. 6, page 13. 


oe 


bein oi “coli 


¥ " 7 ; 
Pals | 4 =? fing “A er 
ie ew 
¥ ON Ny Se 
; om. Sy by, Pineal 
Meee N Ae i 


“ORE eta a 


Ai @ 


Hi ‘ae fe al! Ge roe ty ie ‘ 


J A 
é vit 
oo ahem i) 
* 
: , A 4 A Tm - ‘ 
, ‘ ‘ 
ve ee tk 
~*~ *% “\'y hy 
* 
» 
i 
‘ rY ‘ Del <4 
‘ ig@ Ryo he 


’ t ety \ | / i 
“lod ek on! areas 


~Y 


- ee 8a e +s py Og ® Cees Sen Iewto ee 


se Eres 


14 

Comparing the three cases’ in Fig.6, it is seen that 
curve C which is calculated by equation (9) is nearer to 
the oscillogram than the curve A calculated by equation (6). 
This means that the coefficient of self-induction is chang- 
ing with the saturation of the magnetic core. 

It is interesting to notice that the time to build 
the primary current is a function of the primary resistance 
as well as of the primary inductance. If the resistance 
is higher, the time is shorter, and if the inductance is 
smaller, the time is shorter. But, the resistance should 
not be too large,,because then the primary final current 
is reduced. The inductance Should not be too small, be- 
cause then the secondary peak voltage will be largely re- 
duced in the oscillating discharge. 

If we make the inductance smaller, it is seen that the 
tine to build: the’ current is-largely.reduced as in turve D, 
Fig. 6. 

From the above discussion the following conclusions 


may be drawn ; 


The time to establish the primry current is short 
when L, is small or when y is large. 
With a closed iron core the inductance L,decreases 


as the magnetizing current inccreases. Hence 


the so-called time constant a becomes larger for 


/ 


higher magnetic saturation. 


TO) Sac —aemgaingd 


namie tne ne a 


a ee mn 


a Bee. oa 


ee ee 


es 


~“ 


amore 


TET butls ; Cam te Ma Bid ea: * ts a 


ft, 


os sph: ssh oins ie osuamninees 
eva eh i 


ve Se Ree a kehoann. eT eae 


if ¥a) did Dit Vans Wet £83060 fA, 
ui | “hab 


cr KR Ca Ei Pete nity co lei 


Ae 


1] 


. al ‘ ‘i. 
He ark ATA °S seh 
¢ i}. » ‘ i? ¢ 

j , in 5" } 2 


aD ot 


" woes ot nis hey Vikas bee usu 


H oa r ablsohe 
‘ rr i 
i ) 
¥ wire AN Oy 6, aie? 
: Vu 
‘ V Ft thy 
) uf Gi): 
5 t Liew ef tr i 


aay abe tee mote | fen are A HAN : 
rink. Munley | Lut re ag oilig iaatat : 
Woven yy ales heed mesial with, 


vite! daeptvalee 1 Da tia amet Bite ee 


t 


Py 


tee, ae, 


Caan Soathy) & 


© 
7 


Fig... 7 


The ripples in the current wave seem to be caused by 


the free oscillation of the mirror of the oscillograph. 


' ) A 
i Y , f 1 \ ee - a wy LA \ 
{ J I . _ 7 i 


pac a WOR Rite rane ~ ‘ Pent s 4 eae F< Sa hin le dbs ot Sit all oe tes 4 


a 


sd Roe ey ae 


¢ 
os 


j 
. = _— A hee % = - © 6 aes. - 
rege = cw hie a 


16 


IV Phenomena of Opening 


Interrupter 


a 


\ NAS 
PASAY ATAN 


Nog 
= —— NAN 
4 


Fig., 9 
We assume that the charging current in the secondary 


Then equation (1) becomes 


ssp: dey, Sade 
BAS Re, LAL, et S (7) 


is negligible. 


If we differentiate this equation With respect to t, 


The general solution of this equation is 


a) ee 2 a OTe Aarts 


4 


where m, and. m,are the roots of the auxiliary 


equation. 


za ’ / ah 
C2 ail eee eet as =O 


" 
a 


tatgd “iP wrhononen] 


oo fquiretat 


f 
+ 
' 
a : 
Ob 
ag 
* ~~ 
« 
o 
= 
. 
» 
at 
jr 
i 


try 
«lies so 


f' iE Oe rar 4 4 | wad 3, ¥ ys 


Py, 


f 


. 


Ch OO rae NE < A 
r~ with the primary coil 


is far larger than r 


4 


under the discussion. So it corresponds to case (bd). 


VEE - 


ea ee = + 


: cL 
t= fame go 


4 


A, 2 ty AetP)) 


e"““ A cos At +B sin fo) 


4 


where A and B are integration constants. 


The electro-motive force across the condencer is, 


€c= E-£ p-4 


= ao... 
+tBsingt/+g ae Asinat +Bcos pt] 


ee 


aa 


Pe (ai cay oe Pa RBar ries! tap veil 


Shes ain anne 


i. ¥ a } , : a iA’ iy ov 
Ree Sein ere aul. | ee bance peta bas 


ee oe. 


v 
a 


\ . \ . 
- rm “es 
p* 4 a ‘ 
, 


ce ne . 
a 


¥ 4 m ‘| iM —_= 
1 
; 
= é oi 
4 x na 7 
Pe oo Poh SN ale = A ae} 
¥ > 7. Ayre br Nn, 
; Fm aie? 


, } j ne i 7 i ie toes ies T av (weal tae 


Saas saroch-} ay 


ets wv a ¢ y ; ae | 
if PAT! er 


i kins a eee 


f 


18 


= £-¢@ fae (A coset +B sin gt)- LX(A cospt+Bsingt) 
a L(-A singl+ 8 cosat)/ (7.3) 


i= I where I is the value of the cur- 


at the moment of opening the interrupter. 


rom equation (12) , 
sip = SN 
From equation (13), 


O=E-r,I+L, la+LBg 


(soy Di pad Cam 


Lie Al ee B= B Z 


So, equation (12) becomes 


4, = et { Lcasgt +(F cbs -— B)singt } 


and equation (13) becomes 


- sa E- ol ee ~ ORDTLD singt +In cos at] 


toe 
( see Appendex III ) 
If E is negligible, 


-2 cee (A coset +Bsinpt)-La(A cospl+Bsingt) 
+ BL (-A sinat + B cost) } 


Peat A cos gt +Bsingt) 


oa. ae me 

’ ai 
fy ye “ 7 a ( 
=. one 


J TN be aged Riot iat a 2 Syd becanre ial “nance? aint aden yal gs 
me i 
ia a 


nt Mays Ae sagan ne eh ches a + lees wy “) yee 


A 
A AA | \ Sea ¥ i, Kzesbe yergeayy ts a or vl 
if .) ae 
, . yan a 
a aD we ag ‘baat woes. 

ae he 


iv re The hie dh sd 


eee ism aoe 


, — ‘ Pie o ~ “Vita 
hits ~ aet\ AN tor} 2 Raat b ee a ay BAN it Bs, } mr, j a ar 
- , , ‘ ( " ‘ : 


19 


he Melee 2~“(cosat - Za zine) (16) 


and @. = Para Zr Cos al t+ a Sinjat ee oy Sg cost 


aan / ¢ ‘ 
+L ol, ze Sin Bt— Z pr Sin pt me gS cosgt ) 


_ _ ,-aty -IA tp ya: a f 
=-¢ (ae cas tpi) sinpt 


C17) 


Equations (16) and (17) are reduced by R.Colly in the 


Wiedemann Annalen, vol.44, page 109. 


of 
B in equation (16) is very small in our case. 
, -alt 
So, Sten? A Cost 
af / ; 
€ — ——— 


It is evident that the current and voltage are oscil- 


latory and damped. 
Their period of oscillation is 


a a 3 
ea 


The damping coefficient is equal to Aas 
7 


/ 


VLG; 
o's T=) Bae VLC 


o) —aAE 7 
a 6 Be ee cos 
4 VLC, 


Yd 
, 


(18) 


zt 


-at/Z ee: 
SOT, CED SS 7¥? (19) 
7 = FEC. 


; oy " Ny j a} Fey 4 + i 
} yi ‘9 in Od” Lyeeewee nto il be. Pee 


{ ; 
7 oe 
sae i > .. 
1% 
’ we set cahanr 
i : : ' ra, 
Be cs +, - 
! pane i 
a > ye. % > a: ety ni * oe ‘a 
e Ware i 
% wi dae a 
cide alll E d 
he's - baer “iy 4 -. 
ep aae s eds, 
iy (ee 


If there is Some magnetic leakage in the primary and 


secondary, 
a A,n4 
L, = Ayn 
N= A,n,n, 


Where n,, n, are number of primary and second- 
ary turns. 


If there is no leakage between primary and secondar 
p ’ 


a ee A, 
i S— Li, 
£, max. = fe OS from equation (19) 


ag ke 
and Eamax, = Lo =faal 


because the secondary induced e.m.f. is -m 4 =rsm—t 


(Ze, 
neglecting the damping effect. 
From the above discussion, we may conclude ; 
I The secondary ¢.m.f. is proportional to the prin- 


ary current at the moment of rupture. 


ie Eapaee hh 2 fags) Fly 
5 PIGX. 2 L, Wt, 


if there is no leakage flux. 


Taking 2S example an ignition coil which has following 


constants. 


L, -O11 hénry o 1.1 ohms 
C, 20 nf. 5 S.f2>,. Volts 
I bce amperes 


f { 
‘ \ 
~~ 
* 
) 
a 


ie. A Ya, ¢é 7 y oP ‘f . y 
, Pi eS WE Lutupew 


i i 
‘ 


oe 


era ae, WER 


| 


PG GME GD oe co Va at 
" t ; % 


v ba 7 
~ i ; 2 
i ms ne 4 ' 
a ‘ | a! : i 
1 iad ’ i 
- es val Ait An a t 
j 
f hy ni “\ if dl ’ : 
“A Ph 
4 = a 
yf Sal 
»’ thal 
* y' 
‘ | 
pe » otf 
ior 4 


, rs 
em ie Pr pe a 
£53 ee) ii ALR, wi iit a.) 
7m 7 i i ’ if 
nit 4 a Lier ¢ 1709 aol ha ; @ aa 
te Me : “lay , : J 
; PAN 


21 


ae OY = Etre Set PM Be Achy Saad = 450 
2Z, 2x :O// 
ey I CP Oe a pales Berne ee 77 
a ae, / Gs a PEL OCLMG RED A is 


= / Toe os = 27 OO 
.If L=I4 equation (14) becomes 
te Sylacyes ee 4 
a aa & (Cas pt 2 sth pt) (16) 


AS er Pky 5.2% (COS 2/oo0l- o) 


=) G2 Xe ieee oor 


Table 4 

t ares, cos2100t i 

SEC. ampere 

fe) 1 1 5.2 
-00025 987 -866 4,44 
»0005 °975 5 aa 52 
-00075 962 (@) 9) 
001 0951 = 5 -2.45 
000125 »939 -.866 -4.2 
©0015 -927 -1 -4,.81 
200175 917 - .866 -4.13 
2002 °904 -5 -2.35 
-00225 -883 0 oO 


The corresponding curve is shown in Fig.9, page 24. 


Iff LT =I, equation (15) becomes 


2 pm 
&. = Eres (a ee reos gt] 


ESS STE SS aoe ee 


ee ee 


he 


41> Reo 
; i 


rt Me 


i 
{ % 


1 


hide 
OMS we = 
en en set et ee 


, 
ae 
maoosd fe 


| 


er, es Red nA 
TP we tdanipe 


22 
= $925- Pod -/20 SINR M00b 4+ $: 72 COS Zoot) 


By calculating the terminal voltage at the interrupter 
for each instant, we may determine how the voltage ‘rises up 


and down at the instant of interruption. 


Table 5 

t eee gineoot cos2100t e 

sec. volt 

0 1 fe) 1 fe) 
-00025 987 5 866 60 
20005 -975 866 5 107.4 
-00075 962 1 fe) 121 
-001 2951 «866 -.5 111 
000125 °939 5 ~ 866 66.7 
20015 2927 fe) -1 -11.1 
»00175 917 ~05 - .866 “45 
2002 2904 - 866 ~.5 -89 
.00225 -883 -1 fe) -100 
-00375 “625: > 1 fe) 105 
000525 -769 -1 fe) -86.7 
200675 714 1 fe) 91.5 
200825 »662 =1 @) -73.8 
»90975 614 1 0 79 +3 
001125 -57 - 1 0 -62.7 
001275 053 7 fe) 69.2 
201425 »49 -1 fe) -53.1 
101575 45 1 0 59.7 


i ev ton SOR 4 tants Mn gay ee a, Sas ig 


tnt edd dy Pye EG Le Lh obey ay 
N T° esate Ty kid Stele omy, GRE on vat aed wi ot 
| Pei) peu a pen i 
r . ) wari: aes. i 


a oe focnina TOF Tis SS 


& ay 1 etl t+ 


bites be 
te ae 


at ~ wy 
a lk i 
j (= ee 
| > 5 | ca" 
i oF - ‘ \ 
ii (4 
i ae 7 “ae 
i . 
. f } ; 


a, i a | ri eet OS 11 be tee ' : ' . . 

' . Sb. * | 

f — Pay 

a! , co ia 


i= ey i i 


001725 422 -1 0 m45 
01875 ©3935 1 (6) 52.9 
002025 » 362 -1 0 -37.8 


The corresponding curve is shown in Fig.9, page 24- 


pd 


Bed Mae 


' 
od rh 


ie it ‘ j 


3 


+ “PaSapet 


} 
vy 


i 


, Terke é: ' 
{ or 
‘ 
¢ 
1 
* 
1 
q 


j 

i 
b 
a 
i 


‘ 


——d va e ~ 
“s . 5 4 + 7 } 
; : . ‘ ‘ ze 
\ Fos: 
’ + 


a a a a 
i 
: 
‘. 


j 25 


An experiment to check this calculation was made by 


' inserting a variable capacity into the interrupter terminals 


| 
i of the Connecticut Igniter. 
| The connection diagram for the experiment is shown 
| 
below. 
\ é 
' = <, 
| 
| 
, 
| 
} te er 
| CG XIpterruyple 
j 
| 
| 
! Fig.10 
| 
i 
The voltage at the terminalscof the primary coil 
q ' 
} I 
j e oscillates, by charging and discharging the current to 
| 


he condenser C, after opening the interrupter. 


The oscillogram taken when C= 20 m.f. 


mere pe." s 


- -_.  — 


IAL Med oat Chzbade, oft MG 


oh 4 | Ate iret’ 


ie hi be ‘gape tt 
Wg senate " 


a ir yh 
Big * Mo) 26 Bfan! of ont ge ead il} 
ensloe DP here pert area i ¢ 


apaunetadis od = bee: pee yf? 


leek PW & oP pete, Wee “una 


pee, oa) eee 


2 ay 7 te ities ne es 


re 577 ive 


The maximum peak voltage of the oscillogram is about 
85) volts. 

Comparing, this voltage to the voltage wave of Fig.9 
which has 120 volts in the maximum of the first oscillation, 
we may perceive some difference. It is considered that 
this difference is due to the fact that the energy stored 
in the core is dissipated by the interrupter spark and is 
greatly reduced, while we have not considered this in the 
calculation. 

The period of oscillation agrees in the calculation 
ane the experiment. The period is .003 second per cycle 
by calculation, and the experiment shows us about .0029 


second. 


It is very interesting to notice that if the capacity 


of the condenser is inereased, the oscillating voltage 


induced in the primary coil, as well as the>secondary, is 
is'hower and the period of oscillation is larger. 

The following experimental data shows this fact. 
The current at the moment of opening the interrupter was 
always kept constant, that is 5.2 amperes by making the 


speed same, and G& in Fig.10 was changed. 


Table 7 


Cx Maximum spark length 
Condenser capacity at secondary 


15 Bet. live M»Me 


12 3 
gia | 10 


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27 


Interrupter Spark 


We have so far neglected the interrupter spark where- 
as such a spark always exists with interruption of the 
primary current. This Spark does not occur at the in- 
stant when rupture takes place, but a little later. 

This fact was proved by H.-Armagnat in Eclairage electrique 
(vol xrrl, dganse7. W900, ‘page’ 121°). 

When we break an inductance circuit which is connected 
in Fig.ila, the voltage induced at the interrupter terminals 
does not exactly follow equation (17). 

The capacity between the contacts of the interrupter 
must change from infinity to zero in very short instant. 
When the capacity is infinite, the voltage curve @y, in 
Fig.11 b must be tangent to the absissa. If the contacts 
open wider, the capacity diminishes gradually and the vol- 


tage curve rises along the dotted line. 


The disruptive voltage between the contacts E,’ is 


proportional to the distance between contacts. We assume 


that it rises proportionally to time. 


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29 
The primary spark starts at the intersection of:curves 
BE; and e , but soon disappears. The terminal voltage 
will still rise until the secondary spark appears. 

The voltage continues asilong as the spark exists, 
and drops down when the ionization of air become unstable 
Fig.12(c) shows this phenomenon. The secondary 
spark starts at A and is sustained a short period of time. 
In Fig.12(b), we can not see any spark voltage at 
the secondary which continues a short period as in (c). 

The oscillogram corresponding to Fig.12(c).is shown 


below. 


Voltage variation at the terminals 
of the primary coil with no addition- 
al capacity. 


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Voltage at the terminal of the primary coil 


* 


when there is 20 m.f. capacity 


If we connect a large capacity in parallel with the 


interrupter, we see that the duration of the spark is very 


long, but the disruptive voltage at the secondary is very 


is very small. 


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3 = WY 
- —— she 
4 & 
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BS *} 
.° i ~~ § 
x , - ee Pees 3 | 


VI Opening the Interrupter When 
the Secondary Charging Current 


is Appreciable 


From the oscillographic study, the secondary capacity 
seems to be negligible. But if we consider this capacity, 
the developement of the differential equation is as follows: 


From equations (1) and (2), 


Pepe in Me, oT (a) 
ee eee Zee [se fez 
Ee eide v2 EMO SY (>) 
SES LE RELE LG 4,6, oft* 
Z 
; t AY, elie AG 
ee 22, + 2d, <7 + ly, + i) Ue Pz FE 
Oe ya f, 22 Gye Sy, & SY, 
Bee apy a ere Pel aes 
P. 2 Be BY, fe MC 
ee OM a) aS amar DMA Be ee 
L=2E y w+ h=7e , 2) > Ee, 


The solution of the above simultaneous equations 


are’ 
mo 
Ves Arce 
i (c) 
Vv B Bake ’ 
srs 
where m= -S+# cp 


From (a), (b), and (ce), 


As x42d x eee = p,, xB (I) 
B( x+2hxs y%g*} =v, x°A (II) 


‘y iv iw? 1a ute mi an) i ust Lege 


Nees 10) se Spat ne tite OAR a 
ren 


af 


at im aperneag att = 
oe : 


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ces ap," 7 / hog er 
2 Alle } = ot ak Le, fi). “WW | ‘4 j Ae 5h 


“ Ai Br 
.hS) bed 48) afi od ay 
hh , 


hal 2 2 ey Sa 
s 3% 


. , 
a (tt W ~ ae 
rape a yrtes % = MN + he oy 
os Yh in| % 
J ¥ ‘ah * 4 e ; 
> Dome. os ‘ i Ma” 
~ <. \ >, 
\ a : i es 
* ra ee watt 
s~ 3 


f é iy Comes 4i A V ie wir. Ve Wicemie he a 


7 
f - i 
t . y ae 
a wi 
a nm iy 
 & 
4 
i * roe . Nive 


af {5} Sng oo atays 


a) ; ooo 33 ff Ff syixpeby hae 


0 


33 
The solution of @guations (a) and (b) is 
Via A, 2 + A el + A, es A, em 


es, et Boe 7at+ 8. ah" + B, eo 


eee mt mt mgt, ryt 
cS =mAe +m 4,e t m,A,e + 271,Age 
ea, B. amt P14t- ont mt 
- 42 =m Bem, es om, Byes om, Be 
Where m, is the four roots of the auxiliary 
equation. 


and A and B are constants. 


where “uk 1525554 


From (112, substituting, m for x , 


aes pps 2 
CP 77 te he hing eh) = Fe Pek 


& 
RS ip) ps iD: B, a By. =o 
277, WF), 277 Wg, 


From (II), substituting m for x, 


Zod etde 
a Vg r Mz ) = fa; Ak 


a Me ee reg PAC 


=P 


i. ‘ a A } } 4 
5 , a tye *9 i 
\ ed 
- ie 
A s 
a wo 
a” — 
y * art . ; ~ 
. . , 
bt ee hk 
2 Y a 
r % 
j = 2 ah 
cent 8 2k, 
‘ c 
’ wm. 
» oe 
> cae. 
? , 
‘ 
| 
ay 
rN ‘ i. hi 
ry ( — ee ee 
~~ 


See eer 
bar fs) Z 


a rea PF yee 


tin, @ iain Ae 


. , 
a ren 


i 


34 
By the following four equations 


the boundary conditions, we may find 


Which are derived from 


constant B. 


8. +t 8, + 83 + Ba. = - 
“ee my m3 Wg 
2a) op Ea i 
7, 771, P75 Fie 
B 7 By fs 2, aa 8 3 4 fe = 2 


it t ”, 8, + 971, baz, =o 


B 1 1 1 | P 1 1 1 
Th2 ik mz m8 — ae 3 72 72 
7 ma mz ms a mM m2 me 
ge ih CL yee Poe Eh eae 
m, nm, m, me, Mm, ms Mm 
1 | 1 1 (@) 1 1 
n, ea my 0 m mM, m1, 
; = eos, 2] 1 1 1 oa MR iy i P 1 1 
’ —_ = =~, -——., Ss, ——_ 
“inf m> oy me my mm* 
m, m, m, mh, (a) mM, m, 
az ey 2 a z& 2 
m*, ms ms me @) me My 
pe! tee} 3 3 3 
m mo ma mt @) ms Mm 
Boe 1 1 1 1 a My ms m 
v] 
/ 2 2 2 
a 2 2 2 3 SS 3 
m7 m ms me ma me mi 
3 3 3 3 
m, me my My 
Se 


mm; ml, 1 1 1 


at 


ID 


= -/f? mm, m, 1 1 1 


a mm, 
i hate m~ 
While, 
1 1 1 1 ae a me) fm em) ( mm ~ m,) 
i ae m, Cem) fae m7) (m= whe 
Bip ME: WE) a) Se 
Be tae, aS Me 


I 

v 
3 
B 
B 


B,{m,-m, )(m -m,)(m -m,) 


B, (m,-m, )(m,-m, )(m, -m, ) 


3 
=} 
= 
5 
~ 


{\ 
l 
‘d 
3 
= 
B 
= 


Ae es sade 
B, (a, ma, )(m, m1 )(n, m) 


Il 
t] 
rg 
53 

X 
= 
a 
Ka 
=) 
r 


See ae oe 


if ae a Bert “20/ 


ope 


{I 


A a cos( Ut +co)+Be Ccosi,t+c,) 


‘rr 
i A ; 
* 
, ; My 
} whch | pe lpemey ate 


~~... -_ 
ys Sy. KS 
‘ 1 
i 
a | 
. 


bY 
, 
¢ 
ly 
a 
\ 


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SiS MD hil ia le 
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4 
i) 


3 NY 


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» ) OF 
J's i> hou i 
Pea Wind ee 


36 


100k eat Energy of Various 


Ignition Systems 


The opinion is held by many engineers that if an en= 
eine uns at good speed, the gas can be ignited by a spark 
with comparatively low heat quantity. However, at start- 
ipe of the engine the heat quantity in the spark is an lim- 
portant factor in igniting the mixture. 

The American Bureau of Standards has measured the heat 
in unit sparks for various ignition apparatus Ofraeronautic 
engine by a calorimetric method. (Report No.56) 


A Simplified form of heat measuring apparatus has been 


used by the writer in studying this problem. 


General. Principle 

We introduce a known constant heat energy into a cer- 
tain apparatus and note the rate of temperature rise caused 
by this energy. For this purpose, heat. ereated in a re- 
sistance unit by direct current is accurate. 

Next, we note how ignition sparks in the same apparatus 

temperature of that appratus. 
Comparing the above two effects, we may compute the 


heat quantity in a single spark from the following formula. 


Watts x60 sk 
Spare per rev. X ep... 


Joules per spark = 


is : 
i 
ih 
H | 
.¢ 
a ¢ 
a 
! 
ij 
<< 
m 
? 
al _ . - 


-—— 


= A r ‘ ao ¥ ; cs 4 y ee % x vi a 


{ome Oe hh Bly sic ) of, 2 be 


ee tenth ee | tue © EOE Up mm ely th - oe ve 
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ve 


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> ve ee Pee 
Lane. rie Nel PbO ei 

5 teak ane ene pons a. 


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‘pn f jy fe 
pat te: kL. ane 
ty 
: iad ‘ * 
« " ait 4 OD na 


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sor'san Walid ven ; 
oes Ti; Ma "Le i “a “a co . i 
UPL sin Say nape 
cts, bast Tes oe varia % 


i Mee) " pi iar va ¥ Cid ue bit: ae 


> m went Sat ot gerne tered tas = 
i ae UY I 1) be dd howe: nn | 


aT 


Construction of Calorimeter 

The main part of the calorimeter used in this test 
was made of brass piece set in a double-walled box as 
Shown in Fig.13. 

Thin aluminum plate forms the inside wall and saw- 

is stuffed between the walls so that we may keep in- 

temperature uniform. 

The difference between this method and that of Bureau 


of Standards is that the temperature of the brass wall Was 


measured by thermos-couple in the latter, while in the 


former temperature of cavity inithe brass piece was measured 


by thermometer. 


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Process of Experiment 


First the calorimeter was calibrated. For this pur- 
pose, constant energy was introduced to the cavity for fif- 
teen minutes, readings of the thermometer which measures 
the temperature in the cavity being taken every minute. 

The same initial temperature, 35°C, of the calorimeter 
was always chosen for beginning either a calibration test 
or a spark test. 

The wise of bemperatvure is irregular during the first 
three or four seconds. 

It is supposed that this comes from the fact that the 
initial temperature of the cavity is 35°C, while the tem- 
perature of the=brass piece is not exactly the same as that 
of the cavity. 

To avoid this irregularity, we consider the reading 
at the fourth second as our zero and get calibration of 
the apparatus 2s shown in Fig.135, page 40. 

Several experiments were conducted for different ig- 
nition systems. 

Two different spark gap lengthes were used, a 


and — 


8 
The results of the experiments are show in Figs.1,2,3, 


4, and 5. 


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43 


The energy in unit spark depends greatly upon the 

| primary current at the moment of interruption. Theoretic= 
| ally it is proportional to the square of the current at 
interruption, because the energy stored in induction coil 


E is 
f W — a Pp a 

; 2 

where T # eurrent at interruption. 

We have already seen that the time to build up the 
current in the primary circuit is very slow for the Con- 
necticut Igniter, but very fast for the Atwater Kent system. 
| If we close the primary interrupter permanently, the 


1 final current, which depends upon the resistance of the 


primary coil, is larger in the Connecticut system. 


The following oscillograms shows this relation. 


Primary current of the Atwater Kent system 


| 
| 


| eg aS IRE PEAT RRO PN LS TA = Oe a SL a OR 


Pu 
rey 
Ace 
P 
vw 
" +. 
e 5 
1 
) 
Me 
5 
" 
= 
a Ome 


aa 
a 

sd 
_ 

i 
< 
ed 


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ew | 


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iV aL Skt rae seat 


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rn Bey n 
Ov’? gh 
f 
Ss ee 2 Ms 
rs os) 
‘ 
: 


i, x 
a 


israel adh eat 


A 4o rpm, Drum Speed 
Loo rpm, Tralerrupler Speed 
Sacohdary No Spark 


eee. mee eo] 


Primary current of the Connecticut Igniter 


The Connecticut Igniter must have more energy in unit 
spark at low speeds than has the Atwater Kent. But at 
higher speeds, near 1000 r.p.m. of interrupter shaft (cor- 
responding to 30 to 40 miles per hour of car speed), the 
latter yields more energy per spark. : 

In the Connecticut Igniter, we can get no spark at 
all at more than 1000 r.p.em. (interrupter shaft) for 


4 


see a spark at 1200 r.p.m. or higher and Spark gap. 


co|— 


If we change the spark gap length, it seems that at 


lawespecd, Gheyeneresy le Jattle larger for the larger gap 


length and smaller for the smaller gap length. 


In the Phil Brin Igniter, the heat energy in unit s 


! is large with the high frequency system. But the high 
1 frequency system seems not to be good for the running con- 
| dition of the engine, when we need a rather snappy spark. 
If we use Single spark in this system, the spark energy 
is so small that we can not measure it accurately by the 


calorimeter mentioned above. 


: Single spark of the Phil Brin system 


High frequency spark of the Phil Brin system 


is the duration of the interrupter contact. 
same nature as that of the ordinary induction 


magnetic interrupter. 
& I 


i J ~ - 4 
how small 


cr 


— 
=) 


l = 
nas 


14) 


- 24% 
WLba 


\ 
{ 7 
be a 
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ee (QS) SA stare EE Deeg ae a 
Poets. tye! wee AO me a 
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od aan Livtg.'@ tM ening 
Pd 
} : 
ry 
~ea—n = cr ereag teres nenepenesnsnetepeimstna ct iy 
i ' Ne Peet rae J : 


47 


Appendex 


, dé, At; acne 
ee er ae 8 se 


¢ 


oS tock 


S 


O Pts +t,-29 + Mie + 


Differentiating (1) and (2) with respect to t , 


4 2, Sz’ ‘ 
eee of ee on Pf Sex pte 
Re Ke 4 At2 AL 


A Fa as / 
He hae AG, 42 

=f 2? 44 + M+ 
Se eae Ge res 


= 


and (4) are rewritten the following way. 
2 wells ‘ 
Gah Det 2) <; + 
2 
ee), 


GO) 4, DE + 7D, +E/ 


Br t )y +MQ(EDf+6D.t Z) 4, 


C)x ADS 

Oo = IDE 4, 

The equation for the primary current:f 
o = (LBL tENEQs ED Ee - 


i {(64-mID, * Olt r)D (E+ SZ + ppD, 
4% ly, 
Sr (2 2 Bop) sa 
Cc 9 t ee 


vA 


Similarly, for the secondary current 


0 = (EL-MdDS+ (Olt gles (+B enna 


r coe: 
lige ees Se 


. _ m ‘ 7a 
* a 
, 
\ 
4 + ah 
7 J " 
' 
F 
‘ 
= 
| 


Pee enme'et eileen gna etre 


* , te 


HG 
oo Ve Se - es = 
(E —cr)(1+ki)* F-a'p PRR Gd +ki)4 


~ Albishe) + BU th (E-ir)+ ClE-tr) 
(FEE Cl PALE 
PawAGee hk. 24.8 (0th Ett) + CCE -ir) = / 


4 
it == » the above equation becomes 


eg Je- 2 


ie deve) 


ra 


Y=) 5) vee yee PKE+KE +7* 
PK E)? 


cee (T+hE) 


If we substitute r+kE for a, _ then 


tar rk & 
eee ae end C5 


; f 2 Pr Ar & 
“  (E-ttke® (Eira (1 rkija*” Gree 


50 


Pie 


if (A cospl + Bs/nat)—-La (A cosgl +B singt) 
+ BE, (-A singt +B coset) 


where A=TL anda 


Bette LA 
= ae 


é 


; (ZL) + 1,2 aAP Y 
SC one & eh t ri z Sin Be - Lal cos pl 


| LCE A rae ; 
i a ae sin at ~4 5% svngt + Ir cost 
= In coset + lla cosat 


aie + sinet— eee 
Fe" Ssinatsa tt sinat PEL casat 


+ Gi singe - 
feet ctgpel (CZ 47 <0) kale Cosy 


{I 


Fe fa ox 


ae 
oat sea ie t+LFa 

oft COS Le 

{ 2 a 58 


248 


UNIVERSITY OF ILLINOIS-URBANA 


UE 


3 0112 101352448 


